import matplotlib.pyplot as plt

def sum_1(first,second,n):
    if(n<=0):
        return 0
    if(n<3):
        return 1
    elif(n==3):
        return first+second
    return sum_1(second,first+second,n-1)

sum = 0
for i in range(6):
    sum +=sum_1(1,1,i+1)
print(sum)